Mercury switch



Jan. 31, 1928. 1,658,013

R. W. ARMSTRONG ET AL MERCURY SWITCH Filed Dec. 9

ag/nu WWMM "enemies Jen. a1, 1928.

UNITED STATES "ltdtdllii PATENT OFFICE.

navluonn w. nnius'raoive niun IRA n. MQGABE, or orIIoneo, ItmnoIs; sari)Amu- 'STRONG,ASSIGJZIOR Tl) THE ILLINOIS.

UOZNTAGT CGMPANY, A CORPORATION OF MERCURY swrrcrr.

Application filed December 16, 1922. Serial No. 60'?,303.

The present invention has for its object to improve in certain respectssmall mercury switches that have heretofore already been brought to acomparatively high state of periection. 'ihe mostpractical form of thiskind of a switch is one in which a small body oft mercury is containedin a sealed glass tube having within the same terminals connected tosuitable leadein wires, which a terminals are adapted to be connectedtogether by the mercury when the tube is laid on its side and tipped tothe proper angle. l.hrough "the use of an inert gas in the tube andproperly purified iron terminals, switches of this kind are now enabledto handle currents as great as 10 amperes at 110 volts. Naturally,during the making and breaking of the comparatively heavy cur rents,strong arcs are produced within the switches. invention 'is to produce asimple and novel proportioning of the parts of such mercury switchesthat no arcs that can be formed during the making and breaking of thenormal currents can have any injurious effect or even reduce thesensitiveness of action where sensitiveness is required.

The various features of novelty whereby our invention is characterizedwill hereinafter be pointed out with particularity in the claims; but,-for a fullunderstanding of our invention and of its objects andadvantages, reference may be had to the following detailed descriptiontaken in connection with 3; the accompanying drawing, wherein:

Figure 1 is an elevation of a single-circuit or one-way switch arrangedin accordance with our invention;

Fig. 2 is longitudinal central section through the switch shown in Fig.1, on a somewhat larger scale, in its closed position;

li ig. 3 is a view similar to Fig. 1 showing a double-circuit or two-wayswitch embodying ourinvention;

Fig. 4 is aview, on an enlarged scale, of a fragment of theconnectionbetween a terminal of one of the switches with the correspondingconductor or cable; and

Fig. 5 is a sectiontalren on line 5-5 of Fig. 4-.

Referring to Figs. 1 and 2 of the drawing, 1 represents a glass tubeclosed at the cndsand sealed and containing a small body of mercury 2.Near one end of the tube,

One of the objects of the present and within the same, are two terminals3 and a, spaced apart in the direction of the length of the tube. Theterminals are preferably in the form oi small blocks of iron i'astenedto the inner ends of suitable leading-in wires 5 and 6 that pass throughthe wall of the tube. Thus the terminals may be said to project inwardlyfrom one side of the tube towards the opposite side, from which latterside, however, they are spaced apart. The tube is preferably filled withhydrogen, an inert gas, or any gas which will not react with the mercuryor the terminals 111 a way to decrease the eiliciency of the switch,although this constitutes no part of the present invention. The partsare so proportioned that when the tube is held with its long axisinclined slightly to the horizontal, with the leading-in wires at thetop, the mercury will either lie in the end remote from the tern'iinals,as shown in Fig. 1, or in the end containing theterminals, as shown inFig. 2; electrical connection between the two terminals beinginterrupted in the first position, while in the second positron the twoterminals are electrically connected together.

Generally speaking, all that we have here tofore described is old, ourinvention consisting of refinements which we shall now describe.

hen the switch is tilted from the positron shown in Fig- 1 to that shownin Fig. it the mercury engages the farthest terminal 4t before it doesthe other terminal, the current will ump across the gap between theunderlying mercury and the terminal 3 as soon as this gap becomes smallenough. In other words, the current will flash from the terminal 3 tothe mercury and, where the current is comparatively heavy, the eftect ofthe flash into the middle of the body of mercury sometimes causesadivision of the mercury into two bodies and allows the flash or are tostrike against the underlying glass. Even ii 110- further harm shouldcomb from the action just described it would at least result in afailure of the switch to function in the mostetlicient manner at theinstant when it should function, because the flash and partial or totalseparation of the mercury into two bodies would momentarily delaythecompletion 0:1? the circuit which is closed by the switch. l/Ve havealso found (ill that at times when the switch moves from the closedposition. or. Fig 2 to the open position of Fig. 1 a globule 0t mercuryremains, at least momentarily, to bridge the gap between the twoterminals, so that the circuit is not broken as promptly as it shouldbe. 7

Ve have discovered that the objections just mentioned can be overcome bya simple proportioning of parts which will insure that contact willalways be made first at the terminal and will always be broken last atthis terminal. We therefore form the terminal l with a blunt rounded endand the. terminal 3 with a tapered or pointed end, and locate theterminalfi somewhat closer to, what may be termed the bottom side o'fthe tube than we do the terminal 4:. The result is that when the switchis tipped from the'position shown in Fig. 1 to the other position, eventhough very slowly, the mercury must touch the. pointed end of the oneterminal before it is possible for it to reach the other terminal.Because of the e of thepointed terminal it oli'ers little eslstancet othe movement of the mercury tl'aveling-past it to the other terminal,and therefore the mercury retains its momentum as it approaches thesecond terminal. As soon. as the mercury comes close enough to thesecond terminal an arc may form between the mercury and the terminal;but the force of the arc is. opposed by the entire body or mercuryinmotion and the movement of the mercury will therefore not beperceptibly checked and there will be no delay in completing thecircuit. On the other hand, the same arc, if powerful enough, extending.between the first terminal 51min point perhaps midway between the .endsot'the body of mercury, would break the body otmercurv in two and drivethe parts away from each other, so as not only to delay thefcoinpletion.of. the circuit but also to exposev the glass to the action of the arc.l lz'l' en the switch tipsback towards its open position the mercurydoes notadhere to the p(' inted .terminal as it does to a roundedterminal. Therefore, by makin the terminal t bluntand rounded, themerci: will adhere to the latter asthe switch swings toward. itsopenposition, but is'pe'rmitted by the pointed terminal to stretchitse'lt into an attenuated form until finally the effect of gravitywillfbe suliicient to break the mercury away fromthe rounded contact bya quick snap action; the tube being long, enough to permit the break tooccur betore the mercury strikes theiend of the tube remote from theterminals. Furthermore, the rapidity of theb'reak is not dependent uponthe speed at which the tube is tilted, but the break is always effected,instantaneously, The effect just described is made even more pronouncedby reason of the fact that the arcing is alarea of the latter until thebreak comes.

llhereil'ore, l'recause oil the unique conditions just described in themalrinu and breaking or the circuit, the current-carrying capacity ofour improved switch is very much greater than in previous switches olthis u'eiurral type. due to the fact that the arci upon making andbreaking the circuit is reduced to a minimum and is undcr control. andthe i ""her fact that when the circuit is complete and current'l'lowingr, the cll'cctivc portion of the circuit within the switch isalways or large crossscctional area.

Since the mercury cannot adhere to the pointed tern'iinal because oi theshape ot the latter, and further because it docs not become coated witha film 01 n'iel'cury, all danger oi? having a globulc of mercury remainbridged between the two terminals upon the tilting of the switch to itsopen position, is avoided.

instead of having a singrlocircuit controlled by a switch we may ofcourse control a plurality of circuits; Fig. 3 llustralinu a two-wayswitch, or one controllimi; two cir cuits one of which is always closedwhen the other is open, and vice versa. The tube 8 contains theQlOlllllG of mercury and. in addition to the tcrn'iinals 3 and la oneend. has a sin'iilar set fl and 10 at the other end. The two rounded orblunt terminals arrthe two that are farthest apart, while the pointedterminals lie bctwruzn the other two. 'lfherelorc, whcnercr the cjlobulcol mercury is moving toward either end oi the tube For the purpose o'liconneclilur lopjclhcr thc lcrmiuals in lhat end, it will always one33clirstwith the poin'lcll turninal, which s s ill dead, so that theforce ol :1 llosh will be opposed by the weight andv momcutum ol 'hcentire body oi mercury ll such a llush finally comes between the roundcdl'crminal and the body of mercury, which is the only point at which itcan come.

In Figs i and 5 wehave illust 'ated one of the connections between aleading-in wire and the corresponding terminal. ill reprcsenting abraided tubular conductor into which the end of the leading-in wire islitted. lhe men'iber 11. as shown is made up of two concentric'tuhes orsleeves, but the number of such tubes or sleeves will depend upon theservice to which the comluctor is to be put. The conductor is coveredwith suitable insulating material 12 of any usual or suitable type,which will not intcr'lcre with the flexibility ot the conductor.

neaaoie it While we have illustrated and described with particularityonly a single preferred form of our invention, with a slightmodification, we do not desire to be limited to the exact structuraldetails thus illustrated and described; but intend to cover all formsand arrangements which come within the terms employed in the definitionsof our 1nvention constituting the appended claims.

We claim:

1. A mercury switchincluding a body of mercury and two terminals adaptedto be brought successively into Contact with said mercury and to bedisengaged therefrom in the reverse order, that terminal which is thefirst to make contact with and the last to break contact with themercury being, pointed at the end and the other terminal being blunt atthe end.

2. In combination, a receptacle, a body of mercury in said receptacle,two terminals proiecting downwardly in said receptacle and adapted to bebrought successively into contact with and to be connected together bythe mercury when the receptacle is tipped from one predeterminedposition into another predetermined position, that terminal whicl'i isthelirst to make contact with the mercury when the receptacle is sotipped being pointed at the lower endand the other terminal being bluntat the lower end.

3. In combination, a receptacle, a body of mercury in said receptacle,two terminals projecting downwardly in said receptacle and adapted to bebrought successively into contact with and to be connected together bythe mercury when the receptacle is tipped from one predeterminedposition into another predetermined position, that terminal which is thefirst to make contact with the mercury when the receptacle is so tippedbeing pointed at the lower end and being spaced apart from the bottom ofthe receptacle a lesser distance than the other terminal.

4.. In combination, a receptacle, a'body of mercury in saidreceptacle,two termiterminal which is the first to make contact with the mercurywhen the receptacle is so tipped being pointed at the lower end, theother terminal having a blunt, rounded lower end, and the roundedterminal being spaced apart from the bottom of the receptacle a distancegreater than the distance between the other terminal and the bottom ofthe receptacle.

5. In combination, a sealed tube; two terininals, spaced apart in thedirection of the length of the tube, projecting from one side of thetube near one end thereof partly across the tube, the terminal nearestsaid end of the tube being shorter and having a blunter end than theother terminal; and a small body of mercury in the tube adapted toconnect said terminals together when the tube is held in a predeterminedposition and to lie out of contact with both terminals when the tube isheld in another position.

6. In combination, a sealed tube; two tori'ninals, spaced apart in thedirection of the length of the tube, projecting from one side of thetube near one end thereof and partly across the same, the terminalnearest said end of the tube being shorter than the other terminal so asto be spaced apart from the opposite side of the tube a greater distancethan said other terminal; and a small body of electrical conductingfluid in the tube adapted to connect said terminals together when thetube is held in a predetermined position and to lie out of contact withboth terminals when the tube is held in another position. v

In testimony whereof, we sign this spccilication.

RAYMOND "W. AltlilSllTRONG. IRA E. MGCABE.

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